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Monday, November 12, 2012

Peterbilt 379 & CAT C15

Since I was a child I has been a fan of big trucks, and specially of American style trucks(in Spain is strange to see trucks with long noise).

For this MOC I have chosen one of the most charismatic and representative models of these trucks: a Peterbilt 379.

Also I have endeavored to put a version of CAT C15 engine (I'm also a fan of the brand CAT).

This MOC is made in a 1/10.2 scale, giving a final size of 31 studs width, 99 length and 40 high.

Here you can see some pictures taken in Skaerbaek where you can appreciate the size, there are: this Pete, the Crow's Vampire GT(scale 1:10 too...), the Nathaniel's Supercar and my Veyron.

The total weight is 5.5kg, and has been one of the main problems I've had. Front axles deforms and look like the wheels has huge camber angle. This is a esthetic defect which I hate, but it has not solution if I want to keep all functions and therefore the weight of the truck. I will try to fix it comming soon.

When did the truck I always wanted to do it complete, including the sleeper, but later I had to discard it because the cost would have been huge.

The hood can be raised, and remove if you want removing only 2 axles.

Also if the hood is open, you can remove the steering wheel and before remove the cabin in one piece just pulling up on it. Under the cabin you can find both AA battery boxes and the 4 IR receivers.

The two huge fuel tanks are used to cover part of the mechanisms of the truck: on the left the mechanism of the gearbox and on the right part of the pneumatic system.

As curious data, only the bodywork weight is more than 1 kg...

CAT C15 Engine

Under the hood you can find a replica of the CAT C15 engine, with its 6-cylinder in line.

The engine doesn't have the sides covered to appreciate that the cylinders are located in the same order as the real engine, with 120 ° intervals between them. Getting those 120 º between cylinders was very complicated but I thought it was necessary to be more faithful to the original.

The engine also has a motor M to rotate it, which is connected directly to a battery. Between the engine and the M motor there are a differential, which is also connected to the drive motors, so that the engine is always at idling, but when you starts the drive motors the C15 accelerate adding both speeds. The rotation speeds grow up from 250 rpm up to 700 rpm aprox.

Pneumatic system

After almost 10 years without using pneumatics in any of my MOCs, I decided this was the perfect model to use it.

The pneumatic system the truck runs along the complete truck, mainly controlling the suspension and brakes on all axles.

The pneumatic tube color code is this:
- Blue: general system and suspension
- White: Brakes on
- Black: Brakes off

All pneumatic control is located on the right side of the truck inside the fuel tank.

The pneumatic system starts in the air pumps. A M motor is responsible for operating them asynchronously.
The compressor has auto-stop system, it stops approximately at 2 bars pressure, and restart in 1 bar. This compressor control uses a small cylinder, a PF switch and a small spring to counteract the cylinder. To have enough air to the suspension and brakes the truck has two air tanks, they are located inside the chassis and just above the gearbox.

Also in the cab, between the seats, there is a manometer to measure the system pressure, it is very useful to know how much air have you at any moment.

Axles

As the real truck it has live axles. Both rear axles are driven without differential between them.
In each axle between the differential and the wheel the axls has gear ratio 12/20 to reduce necessary torque in the differential and protect bevel gears.

The front axles uses the same steering system as the real Pete, of course the steering wheel turns too, also it turns 4 laps, again as the real Pete

- Suspension

The suspension is fully pneumatic in all axes, and it doesn't use any spring to help.
The front axle has 4 big cylinder and each rear axle 2.

The cylinder are controlled by a valve connected to the same axes. So that the truck can maintain the height to the floor regardless of the weight above it. If the weight increases the suspension is compressed and the valve opens getting more air into the cylinders, then the suspension turns to stretch and returns to its normal height and the valve closes.
If the weight is reduced same thing happens, the valve opens and lets out some air until the pistons down to the normal position.

- Brakes

The brakes as the real truck are drum brakes, there are a drum on each side of each axle, all of them controlled by a small pneumatic cylinder.
The control of these pistons are made through two valves, one for the front axle and one for the rear axles.

For normal braking the brakes operate all at the same time, but only while you are keeping push the brakes botton.

But you have also parking brake mode, if you push the brakes botton in the opposite direction only rear brakes works, and they will not disabled if you stop pressing botton. To remove the parking brake you only need use the normal brakes.

- Auxiliar output

Behind the cabin there is an auxiliar pneumatic output(blue connector), where you can connect anything you want. The valve to activate it is located before the rear-right wheel

Transmission

The transmission is the biggest mechanism of the truck, and it has an approximate size of 25x7x45 studs.
It uses 4 XL motors for drive.

The transmission has 18+2R speeds(this is true, is not a joke...).

The transmission is divided in two parts: the main gearbox with 9+R speeds with automatic clutch(this gearbox is based on the LR Defender), and a transfer case with 2 speed (H and L)

The main gearbox uses a XL motor to shift gears, it has a speed indicator behind the cabin, and speeds ratio are the next:

Nice. Now th elong wheelbase makes sense: a sleeper would have looked great, but after Denmark and NYC, I understand your hesitance...;-)I especially like the breaking system. What's next? Building it into a wrecker?

in your land rover defender, you had two xl motors going at the same time without having the overload prevention system kick in when you shifted gears. how did you do that? my battery pack doesn't even allow two xl motors.

A result of pure creativity and value-add to details.Respect! I love everything of your work!

I got a question:It´s the first time with a "running" motor, isn´t it?In the description you say, it´s working with a differential. Can you explain it more or even show this function with a picture? (instructions would be the best ;) ). Thanks, Greeting to Spain!

The automatic compressor is a well-known idea. just a cilinder connected to a switch. when pressure goes up the cilinder extend and switch of the power. As a counter force a elastic belt or a spring is attached to te cilinder. A high pressure allows the cilinder to overcome the counterforce. that's all

The crankshaft uses wedge belt wheels to get the 120 degrees. and the rod is made with a ball-axle, an axle connector, a 4L bar and an angle connector.Comming soon I will made some more pictures and instructions for some of the "strange" mechanims of the truck ;)

I considered the 911 as masterpiece, but you proofed us wrong again. Awesome. And I'm proud of myself constructing a real speed/momemtum sensing differential in Lego (always powering a wheel with at least a certain amount of motor-momentum)... Piece of cake!

Sheepo, you mentioned the front suspension results in too much 'Camber' due to excessive weight. How is the front tire connected? Via the axle hole, or via the surrounding pin holes? It seems that the Unimog tire itself is eager to 'bend' when emrely connected via the axle hole...

Anonymous said...Will you make complete instructions for this truck? Would pay for it too ;-)Best build Ive ever seen in my life. Respekt!!January 17, 2013 at 11:41 PM Sheepo said...Maybe in a very far future... but very very far hahahaJanuary 22, 2013 at 5:25 PM

Meanwhile, in the verry verry far distant future .... ;)

I know a little boy who never got a gift for the holidays, whenever he was good he did get a Lego block. After all these years, the boy had enough cubes. But he does not plan anything to do with it until he saw a beautiful truck on the interweb .... the best gift for the upcoming holidays are, of course, the instructions for building a truck. Not any course, but those he saw at Santa Sheepo his site. So please Santa Sheepo, provide us instructions and the following year he will again be a good boy .

and the land-rover, he has since yesterday so that is not an option ;)

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